Mechanical aerosol generator



Aug. 19, 1952 J. W. HESSION, JR

MECHANICAL AERQSOL GENERATOR Filed ma 24, 1944 h 2 5 4 I I INVENTOR J HN W. HESS/0N JR BY fTTORI Aug. 19; 1,952 J. w. HESSION; JR 2,507,743

MECHANICAL AEROSOL GENERATOR Filed May 24, 1944 2 SHEETS-SHEET 2 v INVENTOR JOHN w HESS/0N JR.

gm 54 I 63 A TTORJVEY Patented Aug. 19, 1952 UNITED STATES ATEN T OFFICE 2,607,743 Miio'uaNioah AERosoL GENERATOR- John W. Hession, Jr., ISarien, Conn. Application my 24, 1944-, Serial Ni). 537,176 8' Claims. (oi. 252459) Ii/I yin'ventionrelates to a machine-for the generation of an aerosol composed of any one of various materials and itsdistribution into the atmosphere in the form'of a cloud' useful fora number of purposes; such as theiconcealment of ships at sea, or troops on land or s'ca,or protective operations of th 'e'variousfkinds H The aerosol produced also may be composed of material containing an insecticide capable; for example, of clearing a area 01f m'osquito's or other dangerous insect killing in's'ects damaging to fruits, vegetarian; trees and the like".

Theinvention consists of 'alnaohine preferably power operated, 'whichutilizes heated high velocity combustion ga ses; into which the aerosol material in th formof a" liquid is introduced; to atomize-th'e liduidwithoutinjury thereto into comminuted particles of microscopic and-reasonably homogeneous character; capable of floating asa'cloud in theai'ri U V 7/ H v Mygenerator may be described as a r'notor operated unit comprising preferably a blower or compressor; a; combustion ehamber a mixing chamber connected by a-- Yent'uri passageto the combustion-chamber; a fuel for" gasoline or fuel oil to feed the combustion chamber as well as the motor whcn'of the internal combustion type; a second pump fortheaerosol producing liquid; and a sourcepf cooling waterunder moderate pressure. The'r'riotor drives the blower which delivers air athigh speed into the combustion chamber, the 'air'being'- fed with the fuel oil or gasoline-past a spark plug or ignition electrodes to ignite the air and fuelmixture under suchconditions that the'combustion gases in the combustion chamber have a whirling motion or eddy around an axis; In line with this aizis is a constricted orifice leading from the combustion chamber such; for example, as a Venturi passageway; in which the pressure of the gases is" converted largely to velocity and where an aerosol oil or liquid is' introduced into the combustion gases and' there subject 7 to vaporization as they'travelthrough theVenturi passageway at high Velocity.

Above or beyond the Venturi passageway'is an expansion chamber Where the gases and vapor slow down in speed and increase in pressure, still retaining, preferably; the characteristic whirling motion; after which they are vented through additional constrictions or" Venturi tubes into the air at considerable velocity in an expanding volume; I

Thecombustion gases are rhaintained as devoid of excess air as is practical,- and are given such a high velocity through the Vnturipassageway at the pointwhe're the aerosol liquid is injected as to prevent any appreciate cracking or breaking up of the aerosol liquid. into its component arts, chemically speaking. As" the pressure or the combustion gases is passing through the Vn'turi orifice is converted into velocity, there is a balancing of temperature which completes vaporization and also contributes to preventing the aerosol oil fromc'racb mg.

Figure I is an elevational View partly in section of one form of my apparatus for creating the aerosol.

Figure II is-ajh'o'riionta'l View partly incro'ss section taken on line II+II of Figure I.

Figure III is; an elevational vie taken partly in section of an improved form of my machine.

Figure IV is a horizontal view partly in cross section of the improved machine taken on the line IV IV of Figure III. e H

Figure V 1 53' CI'OSS sectional detail of thefllel oil nozzle v e e The machineja'ss'hown in Figs'I'andII coniprise's" a blower I; adapted to be operated by a motor 2', the belt 3' connecting them turning the blower pulley 4 and driven by the motor pulley 5, these parts" being properly located for the purpose: The'blower'i dlivers' air sufrlcient in-both pressure andvelum'e to create the neededhigh velocity in the constricted passageway" and through the outlets to prevent injury to the aerosol producing ni'aterial; Air pressure preferably about oiiep'o'u'nd ab'"v tmosphere" is erhl. ployed in the machinesshow n in FigspI to-IV. The air pass esthroiigli the blower duct 5 into thecombustion chamber 'i. on the wa th'r'diigh the'duct 6; fuel oil of gasoline; or the hire;- is driventhrough theatomiz'er 1e froih' pipeline 9 by'a fuel pump it! operated by the motor Zfthe fuel pump H3 drawing its supply fronianysuit able source such as a"reser'voir H". A'pre's'sure relief vaive' 12- may" he prbv'ieteu its adjust" the amount of oil delivei ed as the pipe 9; pe'hhiiiih the unused po'rtiofi' to'tr'avel back th ugh the pipe" I3 totlie reservoii' 'i i' Anignition' device Mignites the inixtureof -fuel'oil or gasoline and ainsQthalt th'e'g'as entering the combustion chamber i's'a' resultantgas of combustionf By carefully adjusting 'thelvalve H2; the" requisite ratio of fuel oil qr'gasaiih aha air isarriyed'at so that the cdjfibusii niga's s sii-bsiaiiiiaiiynehtral; it being' un'dersto'od' thatasmah excess" of 3 air is usually unavoidable. The leSs excess air there is, the less injury to the aerosol. In place of combustible mixtures of air and fuel oil or gasoline, any other combustible material may be used. My invention is not limited to this particular means of producing combustion gases, the main requisite being that there shall be a volume of hot gases entering th Venturi sec tion and that they shall be substantially neutral in their effect upon the aerosol producing liquid or other liquid utilized in the machine.

It will be noted by referring to Fig. II that the duct 6 leads into the combustion chamber 1 tangentially so that the gases have a whirling motion, with the axis of the whirl in the particular arrangement shown being off center in the com-' bustion chamber, as indicated in Fig. II by the Position of the tube 15. It is found that when this whirl axis, naturally produced by circular combustion, is also in alignment with the vertical axis of the constriction or Venturi tube iii, the best results are obtained.

One of the objects of this invention is to provide a machine of high efficiency and small size, and if the axis of the whirling action is not in line with the vertical axis of the Venturi tube l6, unnecessary power would be consumed which would require a corresponding increase in size and weight of the machine.

When it is desirable to cool the combustion gases before the introduction of the aerosol liquid, or to cool the aerosol pipe 28, a coil pipe I! may be used as shown in Fig. I, to supply steam to the duct enclosing the aerosol pipe 28. Some of the heat of combustion is imparted to the water in this coil pipe l1, converting it into steam. Water is drawn from the reservoir l8 by a suitable pressure pump [9 to create sufficient pressure to drive the water through the pipe 20 into the coil IT. The water issues in the form of steam through the coil outlet 2| and into the tube I5 to cool the aerosol liquid supply pipe 28 and thereby reduce the dangers of cracking or decomposition into carbon of the aerosol producing liquid as it travels upward through the Venturi passageway [6. A valve 22 in the pipe 20 may be provided to adjust the amount of water supplied to coil I! so that all water is converted into steam in the coil I1 and no water is delivered into the Venturi passageway [6. The aerosol producing liquid is ejected from the nozzle portion 29 of supply pipe 28 and introduced into the combustion gas passing through the Venturi passageway 16.

The aerosol producing liquid and combustion gas mixture flowing through the Venturi passage 16 has a lineal velocity of from 400 to 600 feet a second, which high lineal velocity prevents the aerosol liquid from thermal cracking and discoloring the cloud. Since sufiicient concealing fog is white in color, a discolor-ed cloud would indicate thermal cracking and inefiicient conversion of the liquid to 150%.

Another factor important to the prevention of cloud discoloration is the maintenance of the neutral character of the combustion gases, since excess oxygen would cause combustion of the aerosol producing liquid. Discoloration of the cloud indicates cracking or decomposition of the aerosol producing liquid. Liquid for concealment purposes has low vapor pressure, and useful persistence of the cloud requires that the liquid be neither cracked nor decomposed.

A third factor of operating importance is the production of a large volume of aerosol fog which can be produced from a specified quantity of aerosol producing liquid. My machine produces a large volume of aerosol fog from a given quan tity of aerosol liquid, and will convert to fog approximately its own weight in aerosol liquid in fifteen minutes, and is lighter in weight than the machines heretofore used in fog making.

It will be appreciated, that if a substantial percentage of the aerosol producing liquid is cracked or oxidized or decomposed, there must be a corresponding increase in the load of aerosol oil carried with the machine with which to operate it, and an additional supply of combustion gas producing fuel must also be carried. If the aerosol liquid is cracked, oxidized or decomposed to any appreciable extent, the increased amount of liquid required to produce a fog screen of comparable volume may well be of such proportions as to render the instrument substantially valueless.

Another factor of importance is the degree of opacity of the cloud produced. When the aerosol liquid is cracked, carbonized or decomposed, its opacity is correspondingly reduced so that objects may be seen through it, in which case it loses concealment values. The aerosol fog produced by my machine has a persistent floating effect so that it is able to be borne along by breezes to distant points. My machine combines the many scientific factors required to produce a cloud that will float long distances and be opaque for purposes of concealment.

When the aerosol liquid contains an insecticide, it is also important to avoid cracking and oxidation of the insecticide containing liquid so that the cloud is sufiiciently dense to maintain its insecticide quality, and reduce the volume of aerosol producing liquid which has to be transported for the operation of the machine.

The combustion gas pressures generated are more or less related to the barometer at the point where the machine is used, and when the barometer is substantially different, as at high altitudes, pressures and velocities may be reduced or stepped an average barometer level the combustion gas pressure and velocities may be reduced or stepped up for various purposes so long as their relation remains such as to attain the results set forth. This machine is therefore not limited to the attainment of any specific velocity or pressure, but may be adjusted as operating conditions indicate to produce successful clouds for concealment and/or insecticide purposes.

The aerosol producing liquid is composed preferably of an oil of the type having a relatively high viscosity and low vapor pressure, such as #500 Pale Oil or the like, and is drawn from a reservoir 23 as shown in Fig. I. A pump 24 operated by motor 2 drives the aerosol liquid through the duct 25 into the coils 26 contained in the side and bottom walls of the combustion. chamber and finally to the Valve 21 through the tube 28 to the nozzle 29. The valve 2! or valve 30 in the duct 25 may be adjusted to deliver such a volume of aerosol producing liquid as will be converted into a cloud when ejected into the atmosphere as will now be described, the balance returning to the tank 23 through branch line 25'.

The combustion gas carrying the aerosol producing liquid in vaporized form passes upward from the Venturi passage [6 and into an expansion chamber 3| of such shape and size that the velocity of the gas-vapor mixture is reduced and the pressure increased to effect complete mixing of the combustion products and the aerosol vapor. After mixing in chamber 3|, the combined gas and aerosol liquid .vapor mixture issues through one or more Venturi outlets or nozzles 32 1 into the atmosphere. The speed at which the gaseous vapor mixture issues through the second Venturi outlets or nozzles-i2 determines the rate at which the aerosol vapor is chilled in the atmosphere.

The purpose of the upper expansion chamber 3! is to insure thorough vaporization of the highest boiling point parts of the aerosol oil, which will take longer by a minute fraction of a second than that. required to completely vaporize the lower boiling point parts of the oil, thereby permitting the use of various boiling hydrocarbon oils. A good aerosol producing oil may be described as a high boiling range oil possessed of exceedingly low vapor pressure with the boiling rang rather narrow. The reason the cloud persistsif produced correctly is low'vapor pressure. For example, if. kerosene was put through the machine, it would turn to fogcapable of travelling probably 160 feet. after which it would almost entirely disappear. No. 2 fuel oil would produce a fog which would persist for approximately to 7 of amile. Best. of all is the oil described. above which persistsan indefinite distance.

As the gases pass through, the Venturi passageway it and up through the expansion chamber 3.1, the whirling effect is more or less maintained, assisting in the. more even distribution of the aerosol vapor in. the neutral gases of combustion.

A thermostat 33 may be provided to. indicate the temperature, of the gases in the expansion chamber 3 I. The. various valves may be manipulated to secure the best temperatures in the chamber 31 for producing the cloud, the thermostat facilitating: the correct setting of the various flow and pressure, valves for attaining optimum results.

It willbe noted that this particular form or" apparatusis: suited forlocation near a steam plant for example; such as is used in various steam; driven ships or craft. where the source of pressure is is conveniently supplied from a boiler or fronfiother apparatus as. desired. The combustien chamber 1, Venturi passageway and expalilsiqn chamber 3 i are. preferably surrounded by a double walled casing 34 with insulation 35 between the inner and outer walls. Thus the outer wall retains, its full tensile strength unwealgened from the eiiect of heat Within.

There is shown in FigsIII and IV my improved form of fog generating; machine utilizing as a source of power any suitable prime mover 36, such for example, as an internal combustion engine. This engine drives the pump 31 and the blower 38. The pump 31 may be directly driven by the engine shaft 39 to pump the aerosol liquid from a supply tank 39a in the direction of the arrow through the pipe 48, coil 41 positioned outside of and surrounding the combustion chamber 42, and pipe 43 to the. valve 44. where the aerosol liquid is llplicd to the annular duct 65. around the restricted Venturi passageway 46. The aerosol prodl fi llg .oil in the annular duct 45. enters the Venturi passageway 45 through the holes 4.1, of which there may be. any suitable number to evenly distribute the aerosol oil into the gaspassing up through the passageway 66. The Valve may be used to regulate the amount of aerosol oiladmitted. A pressure valve 68 in line 43 may be provided to regulate the return of such liquid as isnot needed to the supply tank 396;.

The blower38 is driven by its pulley- 59- from the belt driven in turn by the-pulley 51 'onthe engineshaft 39*. The blowrBS-is not shown in 6 detail but may beany suitable blower orcompressor preferably of the centrifugal type. Air from the blower 38 passes through the duct 52 into-the combustion chamber 42 tangentially, to create the whirling motion indicated by thearrows in Fig. IV.

Gasoline or fuel oil is introduced into the pipe 52 by a pressure volume regulating nozzle 53 of any well known type. One form of suitablenozzle 53 is shown in Fig. V having an orifice 54 adjustable in size-to supply the proper amount of gasoline or fuel oil for perfect combustion when ignited by the plug 54a with the volume of air supplied by the blower 38. As such apparatus is never per cent-perfect in attaining combustion, a slight excess of air'such as a few per cent is calculated upon'to get'the combustion as perfect as is practical. Such-a slight excess of air distributed through 'thecombustion gas appears to have no discernible efi'ect or'impairment of the color and quality of the cloud produced. I

The combustion chamber 42 at its upper end is reduced in area to gradually and efficiently convert the'pressure of the gasleaving the combustion chamber into velocity as it passes through the Venturi passageway 46.

The aerosol liquid pumped through the pipe 46 and through the coil M is heated somewhat by the heat of combustion to thereby reduce its vis cosity so that it flows more easily through the valve esand the orificesfifll; at thesame time cooling that portion of the wall of combustion chamber surrounded by-thecoil 41.

The combustion chamber-e2 may be partly immersed in a cooling liquid or water 55 contained in an enclosing-casing 56 so that its walls do not become overheated. The waterin the casing 56 is maintained at the-prop'erlevel by the water level control va1ve;51 connected to the casing 55 We pipecconnection 58. The intake water to thevalve51 is suppliedby a pipe 59 connected to a suitable supply tank 60, the amount of cooling water required being relatively small. A pressure pipe 6| extending from the top of the tank 60 to a source oi pressure such as the high pressure. side 62 of. the blower 38 may be employed to provide the. pressure to cause the water in the tank 60. to ascend through the. pipe 59 into the waterlevel control valve 51, which when openpermits, the. water to flow through the connectingpipe 58 into' the tank 5%. The water in casing; 56;has, the effect of cooling the combustion chamber- 42-, and the water thus heated is partly converted to steam which enters the upper conical portion 63 of the casing 55 tothereby Warm. up the aerosol liquid in the coil AH, after whichthe steam. is vented into the atmosphere through escape port 64. They amountof heat thus lost to. the system is perhaps someni- B. t; u. out of 70 B. t. u. As the combustion gas passes up through the Venturi passageway 46,. the aerosol liquid is introduced into it through the orifices 41 as described; after-which the gas-vapor mixture enters the expansion chamber 65. This chamber has an outer and an inner wall with suitable insulation 65 between them. The velocity of the gasvapor mixture inthe expansion chamberBE is reduced and its pressure increased until the mixture reaches the streamlined outlet nozzles 67 where the mixture issues at high'speedinto the atmosphere.- 'I"he- -press1 ire' of" the gas-vapor mixture in the expansion chamber'65 determines the velocity at which it is ejected into the atmosphere.

Thevelocity of the gas-vapor mixture flowing out ,ofthe nozzles 6'! is important. Too low a velocity results in flaming characteristics which destroy the utility of the mechanism. With the proportions of chamber shown, at sea level, a blower pressure of about one pound maintains a high efficiency throughout the system and this relation of pressure to the final velocity through the orifices 61 is termed the system pressure and is a controlling factor of the efficiency of the machine.

With such pressures and speed through the nozzles 61, there is an ultra rapid chilling and condensation of the aerosol vapor to a point below its flash or fire point, thus forming an opaque cloud. It may be noted that for purposes of concealment the aerosol fog produced should be homogeneous in the matter of particle size, which size should be not less than .3 micron radius nor more than .4 micron radius for best results.

Almost any liquid hydrocarbon will produce a cloud in my machine, though liquid hydrocarbons having low vapor pressures are preferable. For insecticide purposes a suitable light weight poison isadded, in which case the liquid hydrocarbon is the carrier. I have used DDT (dichlorodiphenol trichloroethane) effectively in about the proportion of one part of DDT to 50 parts of liquid hydrocarbon by weight.

It is obvious that the moment the engine 35 is started the whole system is put into full operation, with the creation of the combustion gas in the combustion chamber 42 and the introduction of the aerosol liquid into the Venturi passageway 46. There are no long passageways or coils for the gases to pass through which may cause pressure increase above the point of safety. The amount of heat loss is negligible, and the heat produced is almost entirely applied to the mixing of the aerosol liquid and the gas to effect liquid vaporization and diffusion to the atmosphere. The machine is simple to build and repair and in the smaller sizes can be lifted by manual effort;

This improved fog generator may be constructed to be readily portable and may be used to produce large volumes of cloud for concealment purposes, or for disseminating insecticides. The machine shown in Figs. III and IV is relatively small in size and light in weight, has the capacity to produce large volumes of cloud from a relatively small amount of aerosol liquid and fuel oil, and converts over 95% of the liquid into useful aerosol.

As a combustible oil is usually employed for generating the gases in the combustion chamber, I prefer an engine capable of operating with the same oil as fuel. A gasoline engine meets these objectives, since gasoline is also usable as fuel for the combustion chamber. However, any practicable source of combustion gas may be supplied to the combustion chamber, and the air supply may be provided by any suitable power, the apparatus above described being merely illustrative.

Accordingly, my invention is not limited to the particular elements and forms shown and described, its essential characteristics being set forth in the following claims.

What I claim is:

1. A machine for producing a persistent fog which includes, a throat section having a constricted Venturi type passage, pressure means for forcing a combustion gas through said constricted passage at high lineal velocity, an inlet nozzle for spraying an aerosol liquid into said constricted passage and into said high velocity stream of combustion gas to be vaporized thereby, an enclosed reception chamber connected to the outlet end of said constricted passage for receiving said mixture of aerosol vapor and combustion gas, and a discharge nozzle having a passage leading from said enclosed chamber to the atmosphere through which said vapor and combustion gas mixture is ejected to the atmosphere.

2. A machine for producing a persistent fog which includes, a combustion chamber, means for forcing combustion air and fuel into said combustion chamber, a throat section having a constricted Venturi type passage connected to said combustion chamber whereby the combustion gas from said chamber is projected through said constricted passage at high lineal velocity, an inlet leading into said constricted passage through which aerosol producing material is sprayed into said high velocity stream of combustion gas to be vaporized thereby, an enclosed pressure chamber connected to the outlet end of said constricted passage for receiving said mixture of aerosol vapor and combustion gas, and a plurality of discharge nozzles each having a restricted passage leading from said pressurechamber to the atmosphere through which said vapor and combustion gas mixture is ejected to the atmosphere.

3. A machine for producing a persistent fog which includes, a tapered funnel, a throat section having a constricted Venturi type passage connected to the reduced end of said funnel, means for forcing highly heated combustion gas into the enlarged end of said funnel and through said constricted passage at high velocity, an inlet opening leading into said constricted passage through which aerosol producing material is conducted into said high velocity stream of combustion gas to be vaporized thereby, an enclosed reception chamber connected to the outlet end of said constricted passage for receiving said mixture of aerosol vapor and combustion gas, and a discharge nozzle having a restricted passage leading from said chamber to the atmosphere through which said vapor .and combustion gas mixture is ejected to the atmosphere.

4. A machine for producing a persistent fog including in combination, a combustion chamber, means for forcing a combustible mixture of air and hydrocarbons into said combustion chamber, a tapered funnel having the base end thereof connected to said combustion chamber, a throat section having a constricted Venturi type passage connected to the reduced discharge end of said tapered funnel, an enclosed mixing chamber connected to the discharge end of said constricted passage, means for feeding a liquid aerosol material into said constricted passage whereby said liquid aerosol material is vaporized and suspended in said stream of combustion gas moving into said mixing chamber, and a discharge nozzle having a restricted discharge passage connecting to said mixing chamber through which the aerosol vapor and combustion gas mixture is discharged to the atmosphere.

5. A machine for producing a persistent fog including in combination, a combustion chamber, means for forcing a combustible mixture of air and hydrocarbons into said combustion cham- "tion gas during its passage through said constricted passage whereby said liquid aerosol material is vaporized and suspended in said stream of combustion gas moving into said mixing cham ber, and a plurality of discharge nozzles each having a restricted passageway connecting to said mixing chamber through which the aerosol vapor and combustion gas mixture is discharged to the atmosphere.

6. A machine for producing a persistent fog including in combination, a combustion chamber, a fuel supply line leading into said chamber, means for forcing a controlled supply of air into said combustion chamber whereby a combustible mixture of air and fuel is formed in said chamber, a tapered funnel having the base end thereof connected to said combustion chamber for receiving the combustion gas escaping from said combustion chamber, a throat section having a constricted Venturi type passage connected to the reduced discharge end of said tapered funnel through which the escaping combustion gas is discharged, an enclosed mixing chamber connected to the discharge end of said constricted passage, means for feeding a liquid aerosol material into said high velocity stream of combustion gases during its passage through said constricted passage whereby said liquid aerosol material is vaporized and suspended in said stream of combustion gas moving into said mixing chamber, and a discharge nozzle having a restricted passage connecting to said mixing chamber through which the aerosol vapor and combustion gas mixture is discharged to the atmosphere.

7. A machine for producing a persistent fog including in combination, a combustion chamber adapted to contain a substantially oxygen free combustion gas, a discharge funnel having the base end thereof connected to said combustion chamber through which said combustion gas may escape, a throat section having a constricted Venturi type passage connected to the reduced discharge end of said tapered funnel, pressure means for driving said combustion gas from said pressure chamber, through said funnel and through said constricted passage at high velocity, a nozzle projecting through the wall of said throat section through which liquid aerosol material may be sprayed angularly into said high velocity stream of combusted gas during its passage through said constricted passage whereby vaporization of said liquid aerosol material is effected, an enclosed pressure and mixing chamber of larger internal diameter than the diameter of said constricted passage connected to the discharge end of said constricted passage for receiving the vapor and combustion gas mixture discharging from said restricted passage, and a discharge nozzle connected to said mixing chamber through which the aerosol vapor and combustion gas mixture is discharged to the atmosphere.

8. A machine for producing a persistent fog including in combination, a combustion chamber adapted to produce a substantially oxygen free combustion gas, a discharge funnel having the base end thereof connected to said combustion chamber through which said combustion gas may escape, a constricted Venturi type passage connected to the reduced discharge end of said tapered funnel, pressure means for driving said combustion gas through said constricted passage at high velocity, a heating coil positioned adjacent the wall of said tapered funnel and in heat exchange relationship with the combustion gas discharged through said funnel, an inlet to said coil through which liquid aerosol material may be supplied to said heating coil, an outlet conduit connected to said coil through which the heated aerosol material passing through said coil may be discharged, a nozzle projecting through the Wall of said constricted passage and connected to said discharge conduit through which liquid aerosol material may be projected angularly into said high velocity stream of combusted gas passing through said constricted passage whereby vaporization of said liquid aerosol material is effected, a mixing chamber connected to the discharge end of said constricted passage for receiving the vapor and combustion gas mixture discharging from said restricted passage, and a discharge nozzle connected to said mixing chamber through which the aerosol vapor and combustion gas mixture is discharged to the atmosphere.

JOHN W. HESSION, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,819,184 Macintire Aug. 18, 1931 2,048,997 Collins July 28, 1936 2,173,756 Kronenberg Sept. 19, 1939 2,352,677 Anderson et a1 July 4, 1944 2,364,199 Derr Dec. 5, 1944 2,401,761 Holtham June 11, 1946 2,422,024 Levey et a1. June 10, 1947 

8. A MACHINE FOR PRODUCING A PERSISTENT FOG INCLUDING IN COMBINATION, A COMBUSTION CHAMBER ADAPTED TO PRODUCE A SUBSTANTIALLY OXYGEN FREE COMBUSTION GAS, A DISCHARGE FUNNEL HAVING THE BASE END THEREOF CONNECTED TO SAID COMBUSTION CHAMBER THROUGH WHICH SAID COMBUSTION GAS MAY ESCAPE, A CONSTRICTED VENTURI TYPE PASSAGE CONNECTED TO THE REDUCED DISCHARGE END OF SAID TAPERED FUNNEL, PRESSURE MEANS FOR DRIVING SAID COMBUSTION GAS THROUGH SAID CONSTRICTED PASSAGE AT HIGH VELOCITY, A COIL POSITIONED ADJACENT THE WALL OF SAID TAPERED FUNNEL AND IN HEAT EXCHANGE RELATIONSHIP WITH THE COMBUSTION GAS DISCHARGED THROUGH SAID FUNNEL, AN INLET TO SAID COIL THROUGH WHICH LIQUID AEROSOL MATERIAL MAY BE SUPPLIED TO SAID HEATING COIL, AN OUTLET CONDUIT CONNECTED TO SAID COIL THROUGH WHICH THE HEATED AEROSOL MATERIAL PASSING 